The filter bag media in a baghouse decides how long the bags last, how well dust releases during cleaning, and whether the collector holds its pressure drop or slowly chokes. Picking the wrong fabric is one of the most common reasons bags fail early. This guide covers the media most plants run, where each one fits, and the questions to answer before you order replacements.
Start With Your Operating Conditions
Before comparing fabrics, gather the facts about the gas stream and the dust. Media choice comes down to a few variables:
- Temperature: both normal continuous operating temperature and the highest short-term surge (upsets, startups, burner excursions).
- Moisture: humidity in the gas stream, whether the collector runs near the dew point, and whether condensation forms at startup or shutdown.
- Chemistry: acids, alkalis, oxidizers, solvents, or hydrolysis risk (hot, wet conditions that break down some fibers).
- Dust characteristics: particle size, abrasiveness, stickiness, and whether the dust is hygroscopic (absorbs moisture).
- Cleaning method: pulse jet, reverse air, or shaker. Pulse jet collectors usually use needled felts; reverse air and shaker collectors often use woven fabrics.
If you are replacing bags that performed well, the simplest choice is to match the existing media. If the old bags failed early, blinded, or wore through, treat it as a chance to revisit the specification.
Common Filter Bag Media at a Glance
The temperatures below are approximate continuous-operating limits drawn from general industry references. Actual limits depend on the specific fabric, weight, finish, and the chemistry of your gas stream, so always confirm the rating for your application with your supplier.
| Media | Approx. continuous temp | Moisture / hydrolysis | Chemical notes | Typical uses |
|---|---|---|---|---|
| Polyester felt | Up to about 275°F (135°C) | Fair; can hydrolyze in hot, wet conditions | Fair acid resistance; poor with strong alkalis | General industrial dust, woodworking, cement, grain, metalworking |
| Polypropylene felt | Up to about 170–190°F (77–88°C) | Excellent; does not absorb water | Excellent acid and alkali resistance | Chemical, food, detergent, and damp low-temperature applications |
| Acrylic (homopolymer) | Up to about 265°F (130°C) | Good hydrolysis resistance | Good acid resistance; fair with alkalis | Moist gas streams where polyester would hydrolyze, some dryers |
| Aramid (e.g., Nomex®) | Up to about 400°F (204°C) | Fair; can degrade in hot, wet, acidic gas | Fair acid resistance; good abrasion resistance | Asphalt plants, cement kilns, smelting, hot process dust |
| PPS felt | Up to about 375°F (190°C) | Good hydrolysis resistance | Excellent acid and alkali resistance; vulnerable to high oxygen and strong oxidizers | Coal-fired boilers, waste incineration, other acidic hot gas |
| Fiberglass (woven or felt, usually with a finish) | Up to about 500°F (260°C) | Good | Good acid resistance; poor with alkalis and hydrofluoric acid; poor flex abrasion | High-temperature kilns, furnaces, carbon black; often reverse air |
| PTFE felt | Up to about 500°F (260°C) | Excellent | Excellent resistance to nearly all chemicals | Severe chemical service, incineration, specialty processes |
| PTFE membrane laminate | Limited by the backing fabric | Depends on backing | Depends on backing | Fine, sticky, or high-value dust; low-emission requirements |
| Cotton sateen | Up to about 180°F (82°C) | Fair; supports mildew if kept wet | Poor acid resistance | Shaker collectors, light ambient-temperature nuisance dust |
Nomex® is a registered trademark of DuPont. Aramid felts are also offered under other names.
Finishes and Treatments
The base fiber is only part of the specification. Surface finishes change how dust cakes and releases.
Singed
Singeing passes the felt over a flame to burn off loose surface fibers. The smoother face helps the dust cake release during cleaning and is a common, economical upgrade on polyester and other felts.
Glazed
Glazing presses the felt surface with heated rollers, creating a smoother, slightly sealed face. It can improve release of fine or slightly sticky dust, though a heavily glazed surface may raise initial pressure drop.
Other treatments
- Oil and water repellent: helps with damp or oily dust that would otherwise blind the bag.
- Anti-static: conductive fibers or scrim help dissipate static charge. Where combustible dust is involved, follow your facility’s hazard analysis and applicable codes; media is only one part of that picture.
- PTFE dip or coating: improves chemical resistance and cake release on fiberglass and some felts.
- Acid-resistant finishes: commonly applied to fiberglass for flue gas service.
When to Consider PTFE Membrane
A PTFE membrane laminated to a felt or woven backing captures dust on the surface instead of letting it work into the fabric. That surface filtration generally gives better fine-particle capture and easier cleaning. Membrane bags are worth a look when:
- The dust is very fine and conventional felt blinds quickly.
- Emission limits are tight.
- The product being collected is valuable and you want to recover more of it.
- Pressure drop keeps climbing even with good cleaning.
Membrane media costs more and the membrane can be damaged by abrasive dust or excessive cleaning pressure, so it is not automatically the right answer. The temperature and chemical limits of a membrane bag are set by the backing fabric, so specify both.
Practical Selection Tips
- Leave a margin on temperature. Choose media rated comfortably above your normal operating temperature, and account for surges. Running at or above the limit shortens bag life.
- Watch the dew point. Many failures blamed on media are really condensation problems. Preheating the collector before introducing dust, and keeping the gas above the acid and water dew points, protects almost any fabric.
- Match the cage. Fiberglass and some high-temperature media need cages with more wires or smoother finishes to limit flex wear. Corroded or bent cages damage any bag.
- Consider weight. Heavier felts (expressed in ounces per square yard) generally resist abrasion better, but also affect pressure drop and how the bag fits the cage.
- Keep records. Note the install date, media, and the reason bags were changed. That history is the best guide for your next order.
Information to Have Ready
When asking for a recommendation or quote, it helps to provide the collector make and model, the bag dimensions and top style, the existing media (if known), operating and peak temperatures, a description of the dust and process, and any known moisture or chemical concerns. A used bag or its tag can also help.
Need Help Choosing?
Industrial Filtration has supplied dust collector filter bags and cages to industry since 1956. If you are unsure which media fits your process, or want to match an existing bag or OEM part number, call us at 562-436-4228 or email info@industrialfiltrationinc.com. Send us your dimensions and operating conditions, and we will help you find the right replacement.
